/**
 * @author alteredq / http://alteredqualia.com/
 */
// renderer：渲染器对象  WebGLRenderer.js
THREE.EffectComposer = function(renderer, renderTarget) {

  this.renderer = renderer;
  // 涮锅参数2没有定义，代码自动定义渲染目标
  if (renderTarget === undefined) {

    var parameters = {
      minFilter: THREE.LinearFilter,
      magFilter: THREE.LinearFilter,
      format: THREE.RGBAFormat,
      stencilBuffer: false
    };

    var size = renderer.getDrawingBufferSize();
    // 借助渲染目标对象    即使没有传输响应参数   也可以直接操作参数   不用重新声明变量
    renderTarget = new THREE.WebGLRenderTarget(size.width, size.height, parameters);
    renderTarget.texture.name = 'EffectComposer.rt1';

  }
  //把参数renderTarget赋值给renderTarget1，renderTarget可以来自外部，可以来自内部代码生成
  //renderTarget首次渲染之前，是没有关联帧缓冲区的  渲染一次后，会关联一个帧缓冲区
  this.renderTarget1 = renderTarget;
  // 深拷贝渲染目标
  this.renderTarget2 = renderTarget.clone();
  this.renderTarget2.texture.name = 'EffectComposer.rt2';

  this.writeBuffer = this.renderTarget1;
  this.readBuffer = this.renderTarget2;

  this.passes = [];

  // dependencies
  // 依赖外部文件
  if (THREE.CopyShader === undefined) {

    console.error('THREE.EffectComposer relies on THREE.CopyShader');

  }

  if (THREE.ShaderPass === undefined) {

    console.error('THREE.EffectComposer relies on THREE.ShaderPass');

  }

  this.copyPass = new THREE.ShaderPass(THREE.CopyShader);

};

Object.assign(THREE.EffectComposer.prototype, {

  swapBuffers: function() {

    var tmp = this.readBuffer;
    this.readBuffer = this.writeBuffer;
    this.writeBuffer = tmp;

  },

  addPass: function(pass) {

    this.passes.push(pass);

    var size = this.renderer.getDrawingBufferSize();
    pass.setSize(size.width, size.height);

  },

  insertPass: function(pass, index) {

    this.passes.splice(index, 0, pass);

  },

  render: function(delta) {

    var maskActive = false;

    var pass, i, il = this.passes.length;

    for (i = 0; i < il; i++) {

      pass = this.passes[i];

      if (pass.enabled === false) continue;

      pass.render(this.renderer, this.writeBuffer, this.readBuffer, delta, maskActive);

      if (pass.needsSwap) {

        if (maskActive) {

          var context = this.renderer.context;

          context.stencilFunc(context.NOTEQUAL, 1, 0xffffffff);

          this.copyPass.render(this.renderer, this.writeBuffer, this.readBuffer, delta);

          context.stencilFunc(context.EQUAL, 1, 0xffffffff);

        }

        this.swapBuffers();

      }

      if (THREE.MaskPass !== undefined) {

        if (pass instanceof THREE.MaskPass) {

          maskActive = true;

        } else if (pass instanceof THREE.ClearMaskPass) {

          maskActive = false;

        }

      }

    }

  },

  reset: function(renderTarget) {

    if (renderTarget === undefined) {

      var size = this.renderer.getDrawingBufferSize();

      renderTarget = this.renderTarget1.clone();
      renderTarget.setSize(size.width, size.height);

    }

    this.renderTarget1.dispose();
    this.renderTarget2.dispose();
    this.renderTarget1 = renderTarget;
    this.renderTarget2 = renderTarget.clone();

    this.writeBuffer = this.renderTarget1;
    this.readBuffer = this.renderTarget2;

  },

  setSize: function(width, height) {

    this.renderTarget1.setSize(width, height);
    this.renderTarget2.setSize(width, height);

    for (var i = 0; i < this.passes.length; i++) {

      this.passes[i].setSize(width, height);

    }

  }

});


THREE.Pass = function() {

  // if set to true, the pass is processed by the composer
  this.enabled = true;

  // if set to true, the pass indicates to swap read and write buffer after rendering
  this.needsSwap = true;

  // if set to true, the pass clears its buffer before rendering
  this.clear = false;

  // if set to true, the result of the pass is rendered to screen
  this.renderToScreen = false;

};

Object.assign(THREE.Pass.prototype, {

  setSize: function(width, height) {},

  render: function(renderer, writeBuffer, readBuffer, delta, maskActive) {

    console.error('THREE.Pass: .render() must be implemented in derived pass.');

  }

});
